All of the older evidence is alleged artifacts of human presence - foot prints, stone tools, cut marks, etc.
Studies of modern day DNA, based on known mutation rates, estimate the first human presence in the Americas at 15,000 to 18,000 years ago.
Another article on the History of this Land that maybe of interest.
A DNA Search for the First Americans Links Amazon Groups to Indigenous Australians
July 21, 2015
Helen Thompson